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DRV8301-69M-KIT: InstaSPIN BLDC Commutation

Michael Smith38
Prodigy 20 points
Part Number: DRV8301-69M-KIT

Hi,

I have a DRV8301-69M-KIT to evaluate TI’s solution for control of a brushless DC motor. So far the kit has been used to control both the position and speed of the motor (using InstaSPIN MOTION and a quadrature encoder) - it’s some great software!

I have a question about using InstaSPIN in an environment that has some strict EMI/EMC regulations. Because of these requirements, I’m not sure that conventional “stepped”/trapezoidal commutation (2 phases high/low, 1 phase floating) will be appropriate due to the sharp changes in voltage that can have quite a large frequency response. Firstly, and correct me if I’m wrong, does InstaSPIN by default use this form of commutation? (looking at the voltage going into the motor phases in labs 12x and 13x this looks like the commutation method being used).

Is the smoothest commutation method supported by InstaSPIN SVM? (I saw Chris Clearman's comment in this post: https://e2e.ti.com/support/applications/motor_drivers/f/38/t/298166 and tried out lab 10b, but I think the waveform may still be too choppy). 

And more generally, does TI have any motor solutions specifically aimed at reducing EMI from motor control?

Thanks for your advice,

Michael

  • 0
    TI__Genius 17175 points
    Michael,

    My understanding is that the bulk of EMI from our system would be from the PWM switching, and not from the three-phase current driving the motor. The power stage design would be a bigger concern than the method of control. Even with trapezoidal control, the transitions should be much less severe (and generate fewer harmonics) than the PWM. Have you measured any EMI from the system? I'm wondering if this is more of a precautionary question or one where you've failed a standards test.

    Sean
  • 0 in reply to Sean Bigley
    Prodigy 20 points
    Hi Sean,

    No I haven’t yet measured the EMI from the system (but I will in the coming days). In a previous system (not made using TI’s drivers) there were issues with EMI. In this situation I’m definitely asking as a precautionary measure just to see if there are specific drive techniques made by TI designed to reduce EMI. I'll have a look to see if the PWM switching is producing any substantial signals.

    Thanks for your help,

    Michael.